Sounds good to me. As said before, a long range tank may be beneficial but not essential. If you don't go that way, grab some Willow yellow diesel fuel cans. Don't get the others - the Willow ones have a handle in the side, which as you're emptying the can, makes it much easier to hold. The most we've ever used is 2, but we would always have 4 just in case. That extra 80L was a lot of comfort as the fuel needle approached 'E' and the next town was still a long, long way away!
Driving lights might be handy if you don't get a good distance with your lights now. A UHF radio with a good compromise antenna. A 4.5dB gain antenna is good in the hilly regions but not so good on the flat. A 9dB gain antenna is good on the flat but woeful in hilly areas. The 6dB gain antenna is a nice middle-of-the-road.
An android phone or tablet with "Memoires" app is handy. Take a photo, write some notes, it records location, date and time for you and you can review it later. Consider adding a bluetooth OBD adapter and the android app "Torque" by Ian Hawkins and set up gauges for coolant temp, boost pressure, fuel flow rate, anything else that you think might be useful to keep an eye on. You can also get OSMAND app - Open Street Maps - it's not a bad guide, sometimes better than Google maps and does it all offline, so you don't need 3G access to use it as a navigation tool.
Passengers? You don't mention any, but if it's just you and a partner, consider a small fridge for in the back to keep some cold drinks handy and maybe a sanga or two (we prepare salad rolls for lunch and wrap them in foil, place them in the cooler with 6 cold cans of drink). If there are people in the back, DVD entertainment would be valuable, discourage the use of tablets/books in the back seat to prevent motion sickness over long hauls.
Oh, I find having some hard lollies available while I'm driving for hours quite handy. When I start feeling a little tired and I've only just had a stop and stretch, I grab one lolly and slowly consume it - for some reason my brain goes back to full alertness.
I can't think of much else except to ask that you have a bloody good trip!